1. Field of the Invention
This invention relates to a valve device, and more particulatly to a fluid pressure responsive valve device for on-off controlling a plurality of fluid passages in response to a signal fluid pressure.
2. Description of the Prior Art
Conventionally, various emission control systems for vehicles have been proposed to reduce HC, CO, NOx and the like within the exhaust gases.
These systems will be expected to be operated in response to drive conditions of the vehicle so as to not thereby reduce drivability. Thus, each system has a valve device to thereby independently control the operation of each system in response to drive conditions. This means that each valve has to be arranged within each system and accordingly a complicated piping arrangement will be required. This results in high cost and in complicated pipe construction within a limited space within the vehicle itself.